Our proposed research continuation involves a further search for new photochemical transformations of synthetic utility, the extension of uses of single photon counting methods for determining excited state reaction rates, the further exploration of the chemistry of synthetic organic rods as enzyme-like models, and the study of mechanisms of electronically excited state reactions. In our continuation we plan to explore further the utility of our di-pi-methane rearrangement, that of a new vinylcyclopropene rearrangement giving cyclopentadienes and also that of a "slither rearrangement" in which a three-ring migrates along a pi-system. Our efforts in organic photochemistry aim at a delineation of the factors governing excited state behavior. This goal should lead to enhanced utility of organic photochemistry as a practical synthetic and biochemical tool.